The present invention relates to an electrode for applying voltage to electroviscous fluid, in which viscosity can be controlled by voltage application, and in particular to an electrode for applying voltage to electroviscous fluid, which can be utilized for electric control of mechanical devices such as clutches, valves, shock absorbers, etc..
Electro-rheological fluid or electroviscous fluid, in which viscosity of the fluid is changeable by the application of voltage, has been known for many years (Duff, A. W., Physical Review, Vol. 4, No. 1 (1896) 23). Early studies on electroviscous fluid concentrated on the system containing liquid only, and the electroviscous effect was limited. Later studies were made on the electroviscous fluid of solid disperse system, where considerable electroviscous effect could be obtained.
For example, Winslow proposed an electroviscous fluid, using paraffin, silica gel powder and adding water to make the system slightly electroconductive (Winslow, W. M., J. of Applied Physics, Vol. 20 (1949) 1137). From this study by Winslow, the electroviscous (electro-rheological) effect of the electroviscous fluid is called ER effect or Winslow effect.
The mechanism of thickening effect (ER effect), in the electroviscous fluid has also been studied. For example, Klass reported that each particle in electroviscous fluid, also called the dispersoid generates the induced polarization of the electric double layer, in electrical fields and this was the primary cause of the thickening effect (Klass, D. L., et al., J. of Applied Physics, Vol. 38, No. 1 (1967) 67). If this is explained from the principle of the electric double layer, the ions adsorbed on the dispersoids (such as silica gel) are evenly arranged on outer surface of dispersoid when E (electric field)=0, while ion distribution was deviated when E (electric field)=finite value, and particles exert electrostatic action on each other in an electric field.
Thus, each particle forms a bridge between electrodes and begins to have shearing resistance to stress, resulting in the thickening or ER effect.
However, a metal electrode such as copper is used as the electrode to apply voltage to the electroviscous fluid of conventional type, whereas, when voltage is applied on an electroviscous fluid, constant current flows and an electrochemical reaction on the electrode inevitably occurs by the formation of a bridge along with the dipole formation of dispersoid particles. Therefore, the conventional type electroviscous fluid system inherently has the following problems:
(1) By the consumption of the water, polyhydric alcohol, another substance used as the polarization promoting agent which results from the electrochemical process, electroviscous fluid is electrochemically deteriorated, and the thickening effect is decreased.
(2) By electrochemical reaction, metal electrodes are eluted and corroded, which reduces the durability of the electroviscous fluid system. This imposes serious limitations on the metal electrode such as copper electrode for the electroviscous fluid system.
It is an object of this invention to offer an electrode for electroviscous fluid,, by which it is possible to maintain stable a ER effect up to a high temperature range and to obtain higher durability.